> On Jul 24, 2020, at 9:55 PM, Pavel Stehule <pavel.stehule@gmail.com> wrote: > > SELECT * FROM pg_config;
That doesn't tell me whether or not it can actually be used.
It shows if Postgres was compiled with JIT support.
When you run EXPLAIN ANALYZE SELECT ... then you can see info about JIT overhead. If you don't see notices about JIT in EXPLAIN, then JIT was not used.